[(USGS logo)] U.S. Geological Survey
Water Questions and Answers: Chemical Properties
Select a question that interests you:
1. Why does my water smell like rotten eggs?
2. Why does it take so long to rinse the soap off my hands?
3. How does our swimming pool stay so clean?
4. Why is our porcelain sink stained brown?
5. Why are some lakes I see full of algae and thick plants?
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(1) Q: Why does my water smell like rotten eggs?
A: You would know it if you had this problem! In some parts of the country,
drinking water can contain the chemical hydrogen sulfide, which smells just
like rotten eggs. This can occur when water comes into contact with organic
matter or with some minerals, such as pyrite. The situation mostly occurs as
ground water filters through organic material or rocks.
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(2) Q: Why does it take so long to rinse the soap off my hands?
A: The terms "soft water" and "hard water" are important here. Water is said
to be "soft" if it has a low concentration of calcium and magnesium ions in
it, and "hard" water has a higher concentration. The ions react with the
soap you use to produce a scummy residue that is hard to wash off. If you
use "hard" water you also will have a harder time working the soap up into a
lather. "Hard" water is prevalent in some parts of the country, and
sometimes "water softening" chemicals, that reduce the amount of calcium and
magnesium, are added to the water.
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(3) Q: How does our swimming pool stay so clean?
A: It is not an easy task to keep a swimming pool so clear and clean. If you
just set a pan of water out in the middle of summer you'll see that it fills
up with gunk very quickly. People have to resort to both chemical and
physical means to keep the water clean and safe for swimming. The water is
continuously pumped through a filter to trap particles, like all those bugs
that fall in, and to keep algae and dangerous bacteria from growing,
chemicals such as chlorine are added. Chlorine also is added to your
drinking water to keep those bacteria out of your stomach.
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(4) Q: Why is our porcelain sink stained brown?
A: The brown stain is from too much iron in your water. It is closely
related to simple rust you see on metal, which is iron oxide. Probably the
source of the water you use is ground water, and the water has filtered
through rocks containing iron-rich minerals on the way to the well.
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(5) Q: Why are some lakes I see full of algae and thick plants?
A: First of all, plants naturally grow in and around lakes. Maybe you're
asking about a lake that is being chocked off from so much algae. In many
cases, man is to blame. Actually these lakes are being fed too much food!
There are certain chemicals we use that are nutrients to plants. At our
homes we fertilize our yards with nitrogen, potassium, and phosphorus. These
chemicals wash off our lawns and eventually get into the water system, such
as into creeks, rivers, and lakes. Once there, algae and plants have a feast
on this "food". Things used to be worse for our water bodies. Phosphorus
used to be an ingredient in our laundry detergent, but this has generally
been phased out.
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USGS Water-Use home page
The URL for this page is
http://h2o.er.usgs.gov/public/watuse/wuqa.chemical.html
If you have questions or comments about this document contact
hperlman@usgs.gov
Last modified: 10/11/95
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